Process and plant for pneumatic transport

ABSTRACT

An object (e.g., an elongated vehicle) is displaced through a plurality of end-to-end tube sections each provided at a location adjacent its downstream end with an exhauster which continuously draws air out of the respective section. The downstream end of each tube section is normally closed by a flap-type check-valve arrangement that opens as the object in the tube inertially approaches this downstream end, drawn along by a low-pressure zone created ahead of the vehicle by the exhauster. The presence of the object or vehicle in the tube is detected and an enabling force is applied to the check valve to open the downstream end of the tube and, as the object passes the inlet of the exhauster, it compresses the air captured between its leading end and the check valve. The combined effect of the opening force applied to the valve by the detector as well as the air pressure built up behind it suffice to open this check valve and allow the object to exit from its downstream end of the one tube section and enter the upstream end of the following one, thereby entering the pneumatic-force field of the next exhauster whereupon the cycle is repeated.

United States Eatent n91 Teodorescu et al.

[ PROCESS AND PLANT FOR PNEUMATIC TRANSPORT [75] Inventors: ConstantinGh. Teodorescu; Stefan R Ardeieanu, both of Bucharest, Romania [73]Assignee: lps titut llientru Creatie Stintifica Si Technica-llncrest,Bucharest, Romania 22 Filed: Mar. 28, 1973 21 Appl. No.: 345,722

[30] Foreign Application Priority Data Mar. 31, 1972 Romania 70354 [52]11.5. C1 243/6, 243/4, 243/38 [51] int. Ci. B65g 51/04 [58] Field ofSearch 243/1, 2, 4, 6, 29,30, 243/32, 38, 39; 104/138, 139, 155, 156;105/365 [56] References Cited UNITED STATES PATENTS 461,535 10/1891Johnson 243/6 683,141 9/1901 Pikc 243/38 2,601,391 6/1952 Halpern 243/32X 2,784,922 3/1957 Richert 243/38 3,332,639 7/1967 Joy 243/29 X3,404,638 10/1968 Edwards 104/156 3,438,337 4/1969 Edwards 243/1 X 1Mar. 11, 1975 305,395 5/1918 Germany 243/30 Primary ExaminerEvon C.Blunk Assistant Examiner.lames L. Rowland Attorney, Agent, or Firm-KarlF. Ross; Herbert Dubno [57] ABSTRACT An object (e.g., an elongatedvehicle) is displaced through a plurality of end-to-end tube sectionseach provided at a location adjacent its downstream end with anexhauster which continuously draws air out of the respective section.The downstream end of each tube section is normally closed by aflap-type checkvalve arrangement that opens as the object in the tubeinertially approaches this downstream end, drawn along by a low-pressurezone created ahead of the vehicle by the exhauster. The presence of theobject or vehicle in the tube is detected and an enabling force isapplied to the check valve to open the downstream end of the tube and,as the object passes the inlet of the exhauster, it compresses the aircaptured between its leading end and the check valve. The combinedeffect of the opening force applied to the valve by the detector as wellas the air pressure built up behind it suffice to open this check valveand allow the object to exit from its downstream end of the one tubesection and enter the upstream end of the following one, therebyentering the pneumaticforce field of the next exhauster whereupon thecycle is repeated.

sum 3 5 4} Fig.7

PROCESS AND PLANT FOR PNEUMATIC TRANSPORT FIELD OF THE INVENTION Thepresent invention relates to a system for transporting an object, e.g.,a freight, message or passenger vehicle, through a tube. Moreparticularly this invention concerns a method of and an apparatus forthe pneumatic transport of a container, vessel or the like through anelongated tube.

BACKGROUND OF THE INVENTION A process is known for pneumatic transportinside a tubular passage using vehicles or containers carryingpassengers or goods. Gases under pressure are fed into the passage whichis formed of tube sections having suction-delivery nozzles ofconvergent-divergent shape, and each provided with an annular slotlocated at a small distance upstream the nozzle neck such that the fluidjet, on leaving the slot with great speed, generates along the wall ofthe neck a low-pressure zone which forces the stream to curve towardsthis wall. An air suction of considerably greater capacity is created soas to generate a pressure differential on the one and the other side ofthe annular slot which draws the vehicle downstream while forming aroundit an enveloping rapidly moving air layer which in turn forms a fluidtorus penetrating inside the tube and supporting the vehicle andpreventing it from touching the walls of the tubular passage. The excessfluid escapes through the space between the outer wall of the tube andthe divergent wall of the nozzle. The successive feeding with gas underpressure by the various nozzles along the passage is effected so thatthe vehicle moves on by receiving successive impulses.

This process has the drawback of a reduced stability of the vehicle anddue to the fact that the fluid torus surrounding the vehicle does notsupport the vehicle when the latter exceeds a certain weight, there isthe possibility of blocking the vehicle inside the tube.

A pneumatic device is known for the transport of loads in tubes, bymeans of a container provided with six rollers, two of which are mountedat the lower part, one at each end, to support the weight and transmitit to a central rail mounted at the lower part of the tube, and fourlateral rollers, two at each end, serving to guide the containerdirectly on the walls of the same tube in its straight portions. Oncurves, the tube is also provided with rails for lateral guiding. Thepropulsion of the container is carried out by a mass of compressed airwhich is circulated through the tube to entrain the vehicle, and thebraking is electrodynamic.

The device described above has the drawback that the construction of thecontainer is complicated and the vehicle is very heavy so that a greatdeal of energy is wasted simply in displacing the container rather thanits payload.

OBJECTS OF THE INVENTION It is therefore an object of the presentinvention to provide an improved pneumatic transport system.

Another object of this invention is a transport system wherein theweight ratio of the container to its payload that it can be used totransport people, freight and messages.

SUMMARY OF THE INVENTION These objects are attained according to thepresent invention in a system wherein a plurality of end-to-end(preferably spaced-apart) tube sections are each provided with arespective exhauster. The air in each tube section is continuouslyevacuated therefrom at a location slightly upstream of the downstreamend of the section. An openable check valve or gate is provided at thedownstream end of each such section so that a current of air fromupstream to downstream is created by the exhauster. An object such as afreight container or passenger vehicle is thus drawn toward thedownstream end of the section by the low-pressure zone in front of it,which is substantially lower than the ambient pressure behind it, theupstream end of the tube being open to the atmosphere.

According to another feature of this invention the proximity of thecontainer or vehicle near the downstream end of the tube is detected bya sensor which operates mechanism to apply an opening force to the gateat the downstream end. This force is, however, insufficient to overcomethe pressure differential and spring biasing that hold the gate closed.Only when the container passes the exhauster location (i.e., thelocation at which the exhauster or suction blower communicates with thetube) and starts to act as a ram to compress the mass of air capturedbetween its leading end and the gate is this force sufficient to openthe gate. Since the container develops a relatively rapid rate ofadvance, it has considerable inertia such that it flies past theexhauster to compress the air downstream of it. In this manner thedownstream gate will open only when the container approaches it, therebyinsuring that a malfunction will not open this gate and leave thecontainer stranded in the tube due to a failure of pressure i.e., apressure differential insufficient to move it along.

In accordance with yet another feature of this inventionthe container issupported in the tubes by rollers spaced along the tubes but not carriedon the container, so that this container can be a simple shell.

According to yet another feature of this invention the sensor can be anelectromagnetic coil which coacts with the steel shell of the containerto detect its presence. Alternatively or, in addition, a simplemechanical lever system having an arm extending into the tube can beactuated on passage of the container to detect the presence of thecontainer. It has been found to be advantageous to use this mechanicalarrangement to back up the electromagnetic one so that a safe systemiscreated.

BRIEF DESCRIPTION OF THE DRAWING The above and other objects, featuresand advantages of the invention will become more readily apparent fromthe following description, reference being made to the accompanyingdrawing in which:

FIG. 1 is a schematic diagram of the apparatus according to theinvention with two transport tubes;

FIG. 2 is a longitudinal vertical section through one of the transporttubes;

FIG. 3 is a cross-section taken along line A A, of FIG. 2;

FIG. 4 is a longitudinal horizontal section through the transport tubeat the suction chamber;

FIG. is a cross-section through the transport tube and the container atthe electromagnetic control unit; FIG. 6 is a longitudinal sectionthrough the transport tube showing in enlarged scale the electromagneticand the mechanical control units;

FIG. 7 is a longitudinal section through the force accumulator; and

FIG. 8 is a longitudinal horizontal section through the transport tubeat its downstream end.

SPECIFIC DESCRIPTION The apparatus according to the invention consists,as shown in FIG. 1, of a plurality of transport sections 1 arranged isseries after one another. Each section 1 consists of a tube 11 on whichare mounted a suction chamber 2 connected through a conduit 3 to thesuction mouth of an exhaust fan 4, a check valve 5 operated by theintermediary of two force accumulators 6 and electromagnets 7 which arein turn controlled by an electromagnetic control unit 8. The operationof check valve 5 by means of the same force accumulators 6 may also beperformed by two mechanical control units 9, actuatable by a container10 directly. The mechanical controls 9 ensure the opening of check valve5, if the electromagnetic unit 8 fails to operate owing to someaccident.

The transport section 1 has a tube 11 formed of a number of commercialconduits or pipes connected end-to-end in any convenient airtightfashion, for instance with sleeve joints, so as to form a single tube 11in which a plurality of rollers 12 are mounted by means of bolts 13 andairtight housings 14, as shown in FIGS. 2 and 3. The housings 14 aresecured to tube 11 by means of screws. Each of the rollers 12 projectsthrough a hole a formed in the wall of tube 11 and extends beyond theinner surface of this tube by a distance h so that the container, whilerunning inside the tube 11, only engages the rollers 12 without touchingthe tube wall. The rollers 12 are mounted in sets of three arranged inmutually orthogonal planes, one roller at the base of the tube 11 forsupporting the weight of container 10, and two lateral ones'for guidingthe container 10. The spacing l between the sets of rollers 12 along thetube 11 is chosen dependent on the length l of the cylindrical portionof container 10 and is at most one half this length. The tube 11 isfurther provided with a plurality of slots b at the suction chamber 2 sothat air can be sucked out of this tube therethrough by the exhaust fan4 for the requisite lowpressure zone at the tubes downstream end.

As shown in FIG. 8, the check valve 5 is formed of a fixed partconsisting of a pipe 15, a front wall 16 and two triangular walls 17which are secured to one end of the tube 11 by means of screws. Thetriangular walls 17 are welded to the front-wall 16, in horizontalposition one above the other and spaced so as to allow the container 10to pass between them. Both the front wall 16 and the triangular walls 17have bent edges provided with rubber packings 18. The triangular wallsare stiffened in the position shown by a rectangular frame 19.

The check valve 5 also contains two flaps 20 pivoted on respective axles21, journaled in supports 22.

Normally the movable flaps 20 are biased into contact with the packings18 by two springs 23 and by the low-pressure zone created at thedownstream end of the section 1 by the exhaust fan 4.

. In the open position, shown in dot-dash lines in FIG. 8 and broughtabout by traction on cables 24, the movable flaps 20 leave an aperture ssufficient to let the container pass without hitting them. The maximumsize of the opening s is defined by rubber stops 25 which are fastenedby screws to the rectangular frame 19.

The force accumulator 6, shown in FIG. 7, consists of a tubular housing26 receiving a spring 27 and an end of a rod or bar 28 and connected toan eye 29. The spring 27 is precompressed between the base of theelement 26 and a disk carried on the element 28, the rest position beingdetermined by the latter being locked be means of a countersunk screw 30spanning a notch C out laterally in the threaded boss of the eye 29. Thetubular housing 26 is formed with a hole d which allows air to escape ona sudden tensioning of the spring 27.

The electromagnet or solenoid 7, as shown in FIG. 6,

consists of a core 31 having a movable armature 32 and two coils 33, thewhole assembly being covered by a protective housing 34 on which the twoterminals e and fare mounted.

The electromagnetic sensor 8 which is shown in FIG. 5, consists of atransformer having a primary coil 35 whose terminals i and j areconnected to a power source, a secondary coil 36, whose terminals k andm are connected to the terminals e and fof the electromagnet 7, and aU-shaped core 37. Thus, when container 10 (ferromagnetic object) passesin front of the core 37, the magnetic circuit is closed and asubstantial increase in the voltage in the secondary winding 36 takesplace. The core 37 extends through a hole It formed in the tube 11, sothat the container 10 may pass very near its ends. The whole assembly iscovered by an airtight housing 38.

The mechanical control unit 9, shown in FIG. 6, consists of a two-armlever 39 having at one end a roller 40. The lever 39 pivots around abolt 41, the pivoting angle being limited by two rubber stops 42. Thebolt 41 as well as the rubber stops 42 are fastened to a support 43which is screwed to tube 11, the whole assembly being covered by anotherairtight housing 44.

The connection between the movable armature 32 of electromagnet 7 andlever 39 is made by a cable 45, and between lever 39 and the bar 28 offorce accumulator 6 by another cable 46.

The lever 39 extends inside transport tube 11 with roller 40 through ahole p so that container 10 engages and actuates it when passingthereunder.

The operation of the system, according to the invention, takes place asfollows:

The loaded container 10 is inserted in the upstream tube end.

Exhaust pumps 4 are operated to suck up the air from transport tubes 11,compelling it to circulate through the tube in a single sense from theopen upstream end toward the suction chamber 2 and exhauster 4, thisdownstream end being closed by check valves 5.

When introduction of the container 10 into the interior of transporttube 11 effectively blocks off its free upstream end too, the exhausterevacuates the air in the tube between the container and the check valve5, thus producing and maintaining a low-pressure zone therebetween.

To the upstream side of the container 10 atmospheric pressure will pushthis object 10 into the interior of transport tube 11 toward the suctionchamber 2, this differential force having to overcome the inertia ofcontainer 10, the friction forces between the container 10 and therollers 12 of the transport tube 11, and the resisting forces caused bythe running of the same container 10 due to the level differences of thesoil on which the tube is laid out. Due to the fact that the transporttube ill is provided with rollers 12, the friction forces are a minimumregardless of the total weight of container it). in this way, thecontainer 19 runs through the transport tube 11 and arrives in front ofthe electromagnetic control unit 8 at a relatively high speed. Containerl closes through its steel wall the magnetic circuit without touchingthe core 37, and due to the fact that the primary coil 35 is connectedto line an increase in voltage will be obtained in the secondary coil 36which will actuate the electromagnets 7.

The movable armatures 32 of electromagnets 7 will be attracted and willoperate by means of cables 45 and 46 upon force accumulators 6,compressing spring 27 by means of bar 28. At the same time, the lever 39of the mechanical sensor 9 will also rotate up to the rubber stop 42.The spring 27 will act through the tubular housing 26 on the eyebolt 29and therethrough on the cable 24 to pivot the flap 20 into the openposition. The flaps will not open up suddenly due to their relativelyhigh inertia as well as to the low-pressure zone existing in transporttube 11 between the check valve and the container 10 at the moment whenthis latter is detected by electromagnetic sensor 8 and mechanicalsensor 9.

The front or downstream end of container 10, after passing theelectromagnetic control circuit 8, passes rapidly in front of the slotsb of the suction chamber 2 and covers and blocks them.

Due to its high inertia, the container 10 compresses the air captured inthe transport tube 11 between the suction chamber 2 and the check valve5, acting like a piston. Then the container will pass under withouttouching the rollers 40, since lever 39 is rotated by solenoid 31. Asthe pressure of the air compressed by the container rises towardatmospheric pressure to a level such that the force exerted by spring 27can overcome the resistance of the flaps 20, these flaps will open andthe front end of the container 10 will arrive at the level of the flaps,so that these latter will no longer be able to close. After thecontainer passes entirely, the flaps 20 will close, firstly due tosprings 23 which exert a relatively small closing force, and owing tothe low pressure inside the transport tube ll permanently generated byexhauster 4. After the container passes the flaps 20, it will enter thefollowing transport section 1 of the same system, starting again thecycle described above, but having by this time the initial speed reachedon leaving the first tube. The mechanical control unit 9 backs up theopening control of flaps 2G, in case of an accidental deficiency of theelectric parts. Container 10, by hitting with its conical front endagainst the rollers 40 of lever 39, rotates this lever 39 to tension thespring 27 by means of cable 46 and bar 28. In order to increase theopening safety of flaps 20, the check valve 5 is formed such that theflaps 20 in the closed position lie at an angle equal to the conicity ofthe containers front to that if the container hits them with its conicalportion without previous control, they open up without damage and allowthe passage of the container.

The plant, according to the invention, presents the followingadvantages: It allows the transport with high speed of large weights ofmaterials and goods; the useful conveyed quantity is a maximal one sincethe container is of simple construction and relatively light. Mediumpower stations instead of a single high-power station are used. In theconstruction of the plant it allows the use of helically welded tubes oflarge diameter. It presents a high degree of safety in transport. Itdoes not pollute the atmosphere. It eliminates the influence ofmeterological factors in the transport. it contributes to decongestingthe existing transport means and, finally, it allows the completeautomation of the auxiliary loading and unloading operations.

Each tube 11 may have, as illustrated, a rearwardly flared entry belldisposed just ahead of the check valve of the preceding tube. Thevehicle 10 is preferably elongated with a bullet-shaped or streamlinedend, the length of the vehicle exceeding the distance between the bellof a downstream tube and the check valve end of the preceding orupstream tube. As illustrated, the outer periphery of the vehicle isgeometrically similar to the cross-section of the tube in which it isreceived and this cross-section can be circular, rectangular or square.Sleeve joints may mechanically connect the adjoining ends of successivetubes. The suction chamber 2 surrounds each tube 11 and opens into thelatter via axially extending slots angularly spaced about the tube.

We claim:

1. A system for transporting an object comprising:

a plurality of in-line tube sections, each including:

an elongated tube having an upstream end and a downstream end,

a plurality of rollers mounted at a lower portion and- /or oppositelateral portions of each tube along the interior thereof and uniformlyspaced along the entire length of the tube,

two flaps extending from the exterior toward one another to normallyclose said downstream of said tube by sealing engagement with oneanother, said tube being open at its upstream end;

an elongated objectadapted to traverse said tubes riding on saidrollers;

a device proximal to but spaced from the downstream end of each of saidtubes for creating a lowpressure zone between said downstream end andsaid object for drawing said object from each upstream end toward therespective downstream end of each tube;

means adjacent said device for detecting the proximity of said objectfor applying to each pair of flaps an opening force insufficient toswing said flaps apart and open said downstream end in the absence of anadditional force, but sufficient upon the generation of an over-pressureahead of said object to open said flaps and permit the object to passinto the upstream end of the next following tube, said rollers beingeach sealingly mounted in housings external to said tubes with eachroller penetrating through a hole formed along the wall of the tube,each tube comprises a pair of triangular walls which define with therespective flaps a normally closed gate, said walls being mounted on thedownstream end of the respective tube, and means for pivoting each pairof flaps on the respective downstream end of a tube.

2. A system for transporting an object comprising:

a plurality of in-line tube sections, each including:

an elongated tube having an upstream end and a downstream end,

a plurality of rollers mounted at a lower portion and- /or oppositelateral portions of each tube along the interior thereof and uniformlyspaced along the entire length of the tube, two flaps extending from theexterior toward one another to normally close said downstream of saidtube by sealing engagement with one another, said tube being open at itsupstream end;

an elongated object adapted to traverse said tubes riding on saidrollers;

a device proximal to but spaced from the downstream end of each of saidtubes and creating a low-pressure zone between said downstream end andsaid object for drawing said object from each upstream end toward therespective downstream end of each tube;

means adjacent said device for detecting the proximity of said objectfor applying to each pair of flaps an opening force insufficient toswing said flaps apart and open said downstream end in the absence of anadditional force, but sufficeint upon the generation of an over-pressureahead of said object to open said flaps and permit the object to passinto the upstream end of the next following tube,

a solenoid having an armature;

a first element connected to said armature;

a force storing device connected to said first element, a secondelementconnecting said force storing device to said flaps; and

a pivotal lever engageable with a leading portion of said object andconnected to one of said elements for displacing same.

3. A system for transporting an object comprising a plurality of in-linetube sections each including:

an elongated tube having an upstream end and a downstream end;

at least one outwardly pivotal flap sealingly engageable over saiddownstream end;

means for exhausting air from said tube at a location spacedly adjacentsaid downstream end thereby creating a low-pressure zone at saiddownstream end for drawing said object from said upstream end towardsaid downstream end; and

means adjacent said location for detecting the proximity of said objectand on such detection for applying to said flap an opening forceinsufficient to open up said downstream end whereby said object onpassing said location builds up a relatively highpressure zone adjacentsaid flap which along with said force suffices to open said flap andpermit exit of said object from said downstream end, the detecting meansincluding:

at least one electromagnet mounted on said tube and generating a fieldextending into said tube, said object being at least partiallyferromagnetic,

a solenoid energizable in response to said electromagnet and having anarmature acting upon said flap, and a force accumulator between saidsolenoid and said flap and including a first element connected to saidarmature operatively and a second element connected to said flap. 4. Thesystem defined in claim 3 wherein said tubes are each provided with aplurality of rollers supportingly engageable with said object on passageof same through said tubes.

5. The system defined in claim 3 wherein each tube is provided with apair of such flaps and a pair of triangular walls coating therewith toform a gate, both of said flaps being connected to the detecting means.

6. The apparatus defined in claim 5 wherein said flaps normally lie atan angle to each other, said object having a generally conical leadingend of an apex angle generally corresponding to said angle.

7. The apparatus defined in claim 3 wherein said force accumulatorincludes spring prestressed between said elements.

8. The apparatus defined in claim 3 wherein the detecting means includesa two-arm lever pivoted on said tube and having one arm extending intosaid tube into the path of said object and another arm operativelyconnected to said flap.

1. A system for transporting an object comprising: a plurality ofin-line tube sections, each including: an elongated tube having anupstream end and a downstream end, a plurality of rollers mounted at alower portion and/or opposite lateral portions of each tube along theinterior thereof and uniformly spaced along the entire length of thetube, two flaps extending from the exterior toward one another tonormally close said downstream of said tube by sealing engagement withone another, said tube being open at its upstream end; an elongatedobject adapted to traverse said tubes riding on said rollers; a deviceproximal to but spaced from the downstream end of each of said tubes forcreating a low-pressure zone between said downstream end and said objectfor drawing said object from each upstream end toward the respectivedownstream end of each tube; means adjacent said device for detectingthe proximity of said object for applying to each pair of flaps anopening force insufficient to swing said flaps apart and open saiddownstream end in the absence of an additional force, but sufficientupon the generation of an over-pressure ahead of said object to opensaid flaps and permit the object to pass into the upstream end of thenext following tube, said rollers being each sealingly mounted inhousings external to said tubes with each roller penetrating through ahole formed along the wall of the tube, each tube comprises a pair oftriangular walls which define with the respective flaps a normallyclosed gate, said walls being mounted on the downstream end of therespective tube, and means for pivoting each pair of flaps on therespective downstream end of a tube.
 1. A system for transporting anobject comprising: a plurality of in-line tube sections, each including:an elongated tube having an upstream end and a downstream end, aplurality of rollers mounted at a lower portion and/or opposite lateralportions of each tube along the interior thereof and uniformly spacedalong the entire length of the tube, two flaps extending from theexterior toward one another to normally close said downstream of saidtube by sealing engagement with one another, said tube being open at itsupstream end; an elongated object adapted to traverse said tubes ridingon said rollers; a device proximal to but spaced from the downstream endof each of said tubes for creating a low-pressure zone between saiddownstream end and said object for drawing said object from eachupstream end toward the respective downstream end of each tube; meansadjacent said device for detecting the proximity of said object forapplying to each pair of flaps an opening force insufficient to swingsaid flaps apart and open said downstream end in the absence of anadditional force, but sufficient upon the generation of an over-pressureahead of said object to open said flaps and permit the object to passinto the upstream end of the next following tube, said rollers beingeach sealingly mounted in housings external to said tubes with eachroller penetrating through a hole formed along the wall of the tube,each tube comprises a pair of triangular walls which define with therespective flaps a normally closed gate, said walls being mounted on thedownstream end of the respective tube, and means for pivoting each pairof flaps on the respective downstream end of a tube.
 2. A system fortransporting an object comprising: a plurality of in-line tube sections,each including: an elongated tube having an upstream end and adownstream end, a plurality of rollers mounted at a lower portion and/oropposite lateral portions of each tube along the interior thereof anduniformly spaced along the entire length of the tube, two flapsextending from the exterior toward one another to normally close saiddownstream of said tube by sealing engagement with one another, saidtube being open at its upstream end; an elongated object adapted totraverse said tubes riding on said rollers; a device proximal to butspaced from the downstream end of each of said tubes and creating alow-pressure zone between said downstream end and said object fordrawing said object from each upstream end toward the respectivedownstream end of each tube; means adjacent said device for detectingthe proximity of said object for applying to each pair of flaps anopening force insufficient to swing said flaps apart and open saiddownstream end in the absence of an additional force, but sufficeintupon the generation of an over-pressure ahead of said object to opensaid flaps and permit the object to pass into the upstream end of thenext following tube, a solenoid having an armature; a first elementconnected to said armature; a force storing device connected to saidfirst element, a second element connecting said force storing device tosaid flaps; and a pivotal lever engageable with a leading portion ofsaid object and connected to one of said elements for displacing same.3. A system for transporting an object comprising a plurality of in-linetube sections each including: an elongated tube having an upstream endand a downstream end; at least one outwardly pivotal flap sealinglyengageable over said downstream end; means for exhausting air from saidtube at a location spacedly adjacenT said downstream end therebycreating a low-pressure zone at said downstream end for drawing saidobject from said upstream end toward said downstream end; and meansadjacent said location for detecting the proximity of said object and onsuch detection for applying to said flap an opening force insufficientto open up said downstream end whereby said object on passing saidlocation builds up a relatively high-pressure zone adjacent said flapwhich along with said force suffices to open said flap and permit exitof said object from said downstream end, the detecting means including:at least one electromagnet mounted on said tube and generating a fieldextending into said tube, said object being at least partiallyferromagnetic, a solenoid energizable in response to said electromagnetand having an armature acting upon said flap, and a force accumulatorbetween said solenoid and said flap and including a first elementconnected to said armature operatively and a second element connected tosaid flap.
 4. The system defined in claim 3 wherein said tubes are eachprovided with a plurality of rollers supportingly engageable with saidobject on passage of same through said tubes.
 5. The system defined inclaim 3 wherein each tube is provided with a pair of such flaps and apair of triangular walls coating therewith to form a gate, both of saidflaps being connected to the detecting means.
 6. The apparatus definedin claim 5 wherein said flaps normally lie at an angle to each other,said object having a generally conical leading end of an apex anglegenerally corresponding to said angle.
 7. The apparatus defined in claim3 wherein said force accumulator includes spring prestressed betweensaid elements.